Try this,
The problem may be Desktop Manager's automatic "Check for Updates" feature. This feature uses your internet connection to look for OS updates for your device from your carrier. When it does this it loads a second virtual vendor.xml file in the temp folder on your computer (Vista users look in C:\Users\Username\appdata\virtualstore.) So, even after you delete the normal one that is installed with the OS and Desktop Manager, the automatic "check for updates" feature loads another one based on the brand of device you've got plugged into the PC.

To prevent this from happening this you need to install Desktop Manager WITHOUT this Automatic Update service. Below are the steps to remove this service.

1. Go to Control Panel >Add/Remove Programs.
2. Click on "BlackBerry Desktop Software" and select "Change/Remove."
3. When prompted, hit "Next" and then you should get options for Modify, Repair, or Remove. Choose "Modify."
4. On DM 4.7 and higher, in the list of installed items, you should see "BlackBerry Automatic Update." Click the icon next to it and change it to "This feature will not be available." That should put an "X" next to "BlackBerry Automatic Update." If you are using DM 4.6 or lower and don't see this option in this list then just continue with the install and the installation will ask you a few screens later. A screen will be shown where you will be asked to check the boxes for:

(Note: If you're doing a fresh install of Desktop Manager, be sure and choose the "Custom" install button so that you get the prompt for what features you want installed. Otherwise all the features will be installed as normal and you'll likely run into this issue.)

Once that is complete, you'll need to go back and search your computer for vendor.xml. When you do the search, make sure you click on "Advanced Options" and make sure that you search Hidden files and folders. This is important as some operating systems create a virtual store in the temp folder that this vendor.xml file is located in. You will not find this particular vendor.xml if you don't have hidden files/folders selected for search. Once the hidden vendor.xml is deleted it won't come back if you've reinstalled Desktop Manager without the Automatic Update Feature enabled.

Now, make sure your OS is installed (you may need to install the OS again, if you actually remove Desktop Manager and then reinstall Desktop Manager again. Make sure that you delete the normal vendor.xml file LAST before updating the device.